PITTSBURGH -- Left-hander Jorge De La Rosa, who scuffled before going on the disabled list in April, will rejoin the Rockies' rotation for Tuesday's opener of a three-game road series with the Red Sox.

De La Rosa posted a 10.18 ERA in five starts, made it beyond five innings once, and was nowhere near his best form before the Rockies placed him on the 15-day disabled list with a left groin injury. On Thursday, in his third injury rehab start at Triple-A Albuquerque, De La Rosa threw 94 pitches in seven innings and displayed the fastball usage and efficiency that had been missing.

"All game, I threw a lot of strikes and went to the seventh," De La Rosa said after throwing a side session at PNC Park on Saturday. "The fastball wasn't the only thing I was working on. I was working on a lot of things."

The Rockies plan to start De La Rosa, Jon Gray and Eddie Butler in the series with the Red Sox, which leaves lefty Chris Rusin (1-2, 4.50 ERA) on the outside even though he is coming off one of his better starts -- six innings, two runs on six hits in the Rockies' 3-1 loss to the Cardinals on Wednesday. Manager Walt Weiss said there are many "moving parts" with the Rockies' pitching staff.

Weiss said he is looking for De La Rosa to return to form. De La Rosa is traditionally a slow starter, but some of the struggles this season were alarming even in that context. The rehab assignment had more to do with his pitching than his groin.

De La Rosa strikes out seven

SF@COL: De La Rosa fans seven over 6 2/3 frames

Jorge De La Rosa allows only three earned runs on four hits while striking out seven batters over 6 2/3 innings

"He took care of his business during that time," Weiss said. "We wanted to see more efficiency. He did that. We just wanted him back to being who he is. Obviously, there is a strong track record, maybe not necessarily early this year, but he's got plenty of track record that he can lean on."

De La Rosa spent three seasons in the Red Sox organization before going to the D-backs as part of the deal that sent pitcher Curt Schilling to Boston in 2003. But he never pitched for the big club and, in fact, has never pitched at Fenway Park.

Worth noting

• Rockies Dominican Summer League right-handed pitcher Jose Rodriguez received a 72-game unpaid suspension for testing positive for banned substance Boldenone. The suspension is effective at the start of the 2016 season.

According to MLB.com, the MLB Competition Committee, which met during the Owners Meetings, has broad support for the change. The development was first reported by ESPN.com. The theory is hitters would put more balls in play if umpires didn't call so many strikes on pitches below the knee. Any change would have to be approved by the MLB Playing Rules Committee and the MLB Players Association, but those could be in effect for next season.

"We've been down this road before," Weiss said. "It sounds good at the time, but to actually apply it is tougher than it sounds. These umpires are used to calling certain strikes. That would be a process. It would be interesting to see how that one goes."

• Weiss said the club is considering activating right-hander Jason Motte for the Boston series. Motte hasn't thrown in the Majors this year because of a right shoulder strain.